This essay examines the place of affectivity and emotion in Martin Luther's early theology 1513-25. After a critical discussion of the terminological complexities involved in analysing affectivity and the related category of desire in Luther's Latin writings, it draws on a wide range of Latin and German texts to make an original argument about the origins of Luther's theology of the bondage of the will. It is shown that in developing this theological category Luther regularly used empirical/experiential arguments based on own personal experience of the insuperability of certain sinful affections, and that it is Luther's empirical-theological reflections on the domination of the ratio by the affections – rather than philosophical arguments a...